Low protrusion compensation air bearing
Magnetic head sliders having air-bearing surfaces designed to reduce the protrusion compensation effect. The magnetic head slider includes: at least one front pad located an upstream portion of the slider and operative to generate a lifting force; and a rear pad that is located downstream of the front pad and includes a load-carrying part, for generating a lifting force, and a head mounting part. The head mounting part is separated from the load-carrying part by a groove formed between the load-carrying part and the head mounting part. The head mounting part contains a heat source that generates heat energy and thereby causes a protrusion throw to form on the slider. The groove suppresses formation of the protrusion throw on the load-carrying part and thereby localizes the protrusion throw mostly in the area adjacent to the head mounting part.
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The present invention generally relates to magnetic disk drive devices, and more particularly, to a magnetic head slider for use in a magnetic disk drive.
BACKGROUND OF THE INVENTIONIn order to accommodate and increase the recording density of a magnetic disk drive device, it is important that flying height (or, equivalently magnetic spacing), that is defined as the spacing between a magnetic head mounted in a magnetic head slider and a rotating magnetic disk, is narrowed. An ideal magnetic head slider has a uniform and minimal flying height over the entire surface of the magnetic disk during operation. However, the flying height of a typical slider may have fluctuations caused by the variation of manufacturing tolerance, seek operations and ambient pressure change, such as a drop in atmospheric pressure when operating at a high altitude. Accordingly, some of the magnetic head sliders, referred to as high fliers, may have relatively larger flying heights than an intended average value.
To reduce the flying height of a high flier during operation and thereby to improve the quality of data communication between the magnetic disk and slider, a Thermal Flight Control (TFC) technique (or equivalently, Write Protrusion Control technique) may be used. The TFC technique controls the flying height by use of heat energy generated by heat generating element (or, equivalently, heat source) located adjacent to the writing or recording head. Typically, the heat generating element produces a protrusion throw with a large footprint, about 50 to 200 μm in diameter, wherein the protrusion throw refers to the deformation of the magnetic head slider surface due to the heat energy. The height of a typical protrusion throw ranges from I to 8 nanometers. When the heat generating element is activated, the protrusion throw decreases the magnetic spacing. However, the same protrusion interacts with the air flow beneath the slider surface and increases the magnetic spacing such that the reduction in magnetic spacing generated by the protrusion is diminished. This phenomenon is known as protrusion compensation effect and decreases the efficacy of the TFC technique. In general, low write protrusion compensation is desirable in terms of power consumption of the heat generating element.
A technical challenge to overcome in a typical low compensation design is the undesirable increase in flying height sigma, which is the standard deviation of a flying height distribution, particularly when the magnetic head slider flies at high pitch angles. In general, a large flying height sigma tends to offset the gains in magnetic spacing realized by the TFC technique. As the altitude sensitivity and flying height profile degradation of the slider are associated with the protrusion compensation as well as the flying height sigma, there is a strong need for a technique that can reduce the protrusion compensation effect without significantly increasing the flying height sigma.
SUMMARY OF THE INVENTIONThe present invention provides magnetic head sliders configured to reduce the protrusion compensation effect. The magnetic head slider moves over a magnetic disk that can generate an air flow between the slider and disk during operation.
The magnetic head slider includes: at least one front pad formed on an upstream portion of the slider and operative to generate a lifting force by use of the air flow; and a rear pad that is located downstream of the front pad and along a longitudinal axis of the slider and includes a load-carrying part, for generating a lifting force, and a head mounting part that is separated from the load-carrying part by a groove formed between the load-carrying part and the head mounting part. The head mounting part contains a heat source that generates heat energy and thereby causes a protrusion throw to form on the slider. The groove suppresses formation of the protrusion throw on the load-carrying part and thereby localizes the protrusion throw mostly in the area adjacent to the head mounting part.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
When an airflow generated by the rotation of the magnetic disk 12 enters between the magnetic head slider 14 and the magnetic disk 12, pressure is generated therebetween, so that the magnetic head slider 14 begins to float off the surface of the magnetic disk 12. The magnetic slider 14 is designed to float with such an attitude that the flying height on the flow-in side is larger than the flying height of the flow-out side, i.e., the magnetic head slider 14 has a slight pitch angle a so that the head 20 is closer to the magnetic disk 12 during operation than is the remainder of the slider.
The graph 28 in
As suggested by graph 28, some sliders have large flying heights and are referred to as high fliers. To reduce the flying height 22 during operation, the distal end portion of the slider 14 may be controlled by the Thermal Flight Control (TFC) technique (or equivalently, Write Protrusion Control technique). The writing element of the head 20 includes a coil for generating a magnetic field when recording data in the storage elements 24. The slider 14 includes a heat generating element or heat source (not shown in
In
The shape and depth of each surface constituent in the air-bearing surface 38 is determined to meet the design requirements, such as flying height uniformity across the radial direction of the disk, sensitivity of the flying height with respect to atmospheric pressure change, magnitude of the flying height sigma, fly height loss during track seek, fly height change during servo track writing, and dynamic stability of the slider. The front pads 44, load-carrying part 51, fourth surface constituents 40 and head mounting part 52 are formed at a first surface level positioned most closely adjacent to the magnetic disk 12. The first surface constituent 48, third surface constituent 56 and the fifth surface constituents 42 are formed at a second surface level further separated from the magnetic disk 12 than the first surface level. The second surface constituent 46 is formed at the third surface level even further separated from the magnetic disk than the second surface level. The slider 14 may further include a sixth surface constituent 67 located downstream of the head mounting part 52, wherein the sixth surface constituent may be formed at the second surface level.
Each of the first to third surface levels contains one or more surface constituents and has a preset amount of difference in depth with respect to its neighboring surface level. Each surface may have a slight variation in level or depth. For example, as the hardness of the base material (TiAlC) constituting the first portion 16 (
It is noted that the head mounting part 52 is separated from the load-carrying part 51 to reduce the protrusion compensation effect. Further detailed description of the circled portion 54 containing the rear air-bearing pad 50 is given in connection with
FIG. S is a cross sectional view of the circled portion 54 depicted in
The depth d1 from the first surface level to the second surface level is about, but not limited to, 0.05-0.5 μm, and the depth d2 from the second surface level to the third surface level is about, but not limited to, 0.5 to 5 μm, respectively. As such, the depth of the groove 53 ranges from 0.55 to 5.5 μm and is preferably 1.5 μm. It is noted that the present invention could be practiced with any suitable range of the depths d1 and d2, and with any suitable dimension of the head mounting part 52. It is also noted that the depth of the groove 53 is same as that of the second surface constituent 46.
As in the case of the embodiment illustrated in
Again, it is noted that the head mounting part 86 is separated from the load-carrying part 85 by trench or groove 98 to localize the protrusion throw in the area adjacent the head mounting part 86 and thereby to reduce the protrusion compensation effect. Further detailed description of the circled portion 88 containing the rear air-bearing pad 84 is given in connection with
As illustrated in
As depicted in
Table 1 shows dynamic characteristics of sliders having various air-bearing surface configurations under an exemplary operational condition. The first column corresponds to a typical magnetic head slider without separation of the load-carrying part from the head mounting part. The second and third columns respectively correspond to the first and second embodiments illustrated in
The fifth row shows the flying height loss due to a drop in atmospheric pressure during operation at the altitude of 10,000 ft. As can be noticed, the altitude sensitivity or loss at 10,000 ft is well preserved for both embodiments. In fact, the second embodiment has an improved response to the pressure change. Also, as shown in the sixth row, the flying height sigma is well preserved for both embodiments.
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
Claims
1. A magnetic head slider configured to move over a magnetic disk to write data thereto and read data therefrom, the disk being capable of generating an air flow between the disk and the slider during operation, the magnetic head slider comprising:
- at least one front pad formed on an upstream portion of the slider and operative to generate a lifting force by use of the air flow;
- a rear pad located downstream of said front pad and along a longitudinal axis of the slider and including a load-carrying part for generating a lifting force by use of the air flow and a head mounting part that is separated from said load-carrying part by a groove formed therebetween, said head mounting part including a heat source that generates heat energy and thereby causes a protrusion throw to form on said slider,
- wherein said groove suppresses formation of said protrusion throw on said load-carrying part.
2. A magnetic head slider as recited in claim 1, wherein said head mounting part has a shape elongated in a direction transverse to the longitudinal axis.
3. A magnetic head slider as recited in claim 2, wherein said head mounting part has a length of about 25 μ and a width of about 70 μm in the transverse direction.
4. A magnetic head slider as recited in claim 1, wherein a trailing edge of said head mounting part is shaped to have a level approximately matching an outer boundary of a footprint of said protrusion throw.
5. A magnetic head slider as recited in claim 1, further including:
- a first surface constituent adjacent said front pad and operative to compress the air flow; and
- a second surface constituent adjacent said first surface constituent and operative to generate a sub-atmospheric pressure thereon,
- wherein said front and rear pads are formed at a first surface level, said first surface constituent is formed at a second surface level, and said second surface constituent and said groove are formed at a third surface level and wherein said first, second, and third surface levels are formed sequentially from an adjacent side to said magnetic disk.
6. A magnetic head slider as recited in claim 5, wherein the depth from the first surface level to the second surface level ranges from 0.05 to 0.5 μm, and the depth from the second surface level to the third surface level ranges from 0.5 to 5 μm.
7. A magnetic head slider as recited in claim 5, wherein said front pad includes two side parts respectively located on opposite sides of the longitudinal axis.
8. A magnetic head slider as recited in claim 5, further comprising:
- a pair of side air-bearing pads respectively located on opposite sides of the longitudinal axis and adapted to increase air-bearing stiffness of said slider, each said side air-bearing pad including: a third surface constituent having a generally rectangular shape; a fourth surface constituent having a substantially polygonal shape with an elongated portion, a tip of said elongated portion being in contact with said third surface constituent; a fifth surface constituent partially surrounding said third and fourth surface constituents and forming a tail of said frond pad; and a sixth surface constituent partially surrounding said fifth surface constituent and forming a tail of said first surface constituent,
- wherein said third surface constituent is formed at said third surface level and said fourth surface constituent is formed at said second surface level.
9. A magnetic head slider as recited in claim 1, wherein said head mounting part further includes a head for writing data to and for reading data from the disk.
10. A magnetic head slider configured to move over a magnetic disk to write data thereto and read data therefrom, the disk being capable of generating an air flow between the disk and the slider during operation, the magnetic head slider comprising:
- one front pad formed on an upstream portion of the slider and operative to generate a lifting force by use of the air flow;
- a rear pad located downstream of said front pad and along a longitudinal axis of the slider and including a load-carrying part for generating a lifting force by use of the air flow and a head mounting part that is separated from said load-carrying part by a groove formed therebetween, said head mounting part including a heat source that generates heat energy and thereby causes a protrusion throw to form on said slider, wherein said groove suppresses formation of said protrusion throw on said load-carrying part;
- a first surface constituent adjacent said front pad and operative to compress the air flow;
- a second surface constituent adjacent said first surface constituent and operative to generate a sub-atmospheric pressure thereon, wherein said front and rear pads are formed at a first surface level, said first surface constituent is formed at a second surface level, and said second surface constituent and said groove are formed at a third surface level and wherein said first, second, and third surface levels are formed sequentially from an adjacent side to said magnetic disk; and
- a pair of side air-bearing pads respectively located on opposite sides of the longitudinal axis and adapted to increase air-bearing stiffness of said slider, each said side air-bearing pad including: a third surface constituent having a generally rectangular shape; a fourth surface constituent having a substantially polygonal shape with an elongated portion, a tip of said elongated portion being in contact with said third surface constituent; a fifth surface constituent partially surrounding said third and fourth surface constituents and forming a tail of said frond pad; and a sixth surface constituent partially surrounding said fifth surface constituent and forming a tail of said first surface constituent, wherein said third surface constituent is formed at said third surface level and said fourth surface constituent is formed at said second surface level.
11. A magnetic head slider as recited in claim 10, wherein said head mounting part further includes a head for writing data to and for reading data from the disk.
12. A magnetic head slider configured to move over a magnetic disk to write data thereto and read data therefrom, the disk being capable of generating an air flow between the disk and the slider during operation, the magnetic head slider comprising:
- two front pads respectively located on opposite sides of a longitudinal axis and operative to generate a lifting force by use of the air flow;
- a rear pad located downstream of said front pads and along a longitudinal axis of the slider and including a load-carrying part for generating a lifting force by use of the air flow and a head mounting part that is separated from said load-carrying part by a groove formed therebetween, said head mounting part including a heat source that generates heat energy and thereby causes a protrusion throw to form on said slider, wherein said groove suppresses formation of said protrusion throw on said load-carrying part;
- a first surface constituent adjacent said front pads and operative to compress the air flow; and
- a second surface constituent adjacent said first surface constituent and operative to generate a sub-atmospheric pressure thereon, wherein said front and rear pads are formed at a first surface level, said first surface constituent is formed at a second surface level, and said second surface constituent and said groove are formed at a third surface level and wherein said first, second, and third surface levels are formed sequentially from an adjacent side to said magnetic disk.
13. A magnetic head slider as recited in claim 12, wherein said head mounting part further includes a head for writing data to and for reading data from the disk.
Type: Application
Filed: Mar 31, 2006
Publication Date: Oct 4, 2007
Patent Grant number: 7593188
Applicant: Hitachi Global Technologies Netherlands, B.V. (Amsterdam)
Inventor: Oscar Ruiz (San Jose, CA)
Application Number: 11/395,555
International Classification: G11B 5/41 (20060101); G11B 5/60 (20060101);